The present invention relates in general to metal-forming, and, more specifically, to improved forming tools such as drawing/stamping dies with the ability to manipulate metal flow patterns during drawing.
Sheet metal forming is used in many industries, including in the manufacture of automotive body panels and structural components. One commonly used process uses stamping dies having a punch side and a cavity side with matching surface contours. During stamping, metal is drawn into a desired shape as defined by the contoured surfaces. The material of the sheet metal flows over the die surfaces as it bends and stretches under the forces applied by the drawing together of the die surfaces.
Significant engineering effort is necessary to design a metal-forming manufacturing process. A designer determines the die surface contours, the locations and strength of binding elements, and the size and shape of the metal blank, for example. When the desired shape of a manufactured component has steep or complex bends, it may be difficult to design dies that avoid the tendency for the metal to flow too much in one direction and not enough in another direction. Without proper flow, some regions may not achieve a desired thickness during drawing. In particular, an area of the finished (i.e., stamped) component may be too thin because of a net flow away from that area.
Friction between the die surfaces and the flowing metal sheet results in wear of the die surfaces. The dies have a limited tool life as a result of wear. Thus, it would be desirable to reduce friction between the tools and the workpiece in order to enhance tool life.